Since the first discovery of carbon nanotube (CNT) by a Japanese scientist Lijima in 1991; in particular, since the discovery of monolayer CNT and the success in the large amount synthesis of CNT. CNT has aroused wide interest and has been a major research field of fullerene family. It is also one of the most cutting-edge research areas in the disciplines of physics, chemistry and materials science. Because of its unique structure, the study of CNT is of great theoretical significance and has many potential applications, For example, its unique structure is an ideal model of one-dimensional material; its large aspect ratio is expected to be used as tough carbon fiber, and its intensity is 100 times as tough as steel, whereas the weight is only ⅙ of steel; In addition. It also can be potentially used as molecular wire, nano-semiconductor material, catalyst support, molecular absorbent and near field emission material, and so on. Scientists believe that CNTs have sonic applications as follows: hydrogen storage materials, field emission, new type of carbon fiber and reinforcing materials, supercapacitor electrode, electronic probe, a new generation of electronic devices, lithium-ion battery electrode materials, stealth material, catalyst components, CNT muscle, polymer CNT composites, blending materials, synthesis within the CNTs, soluble reagents, the cleaning of radioactivity, the separation of isotope, and so on.
There are many methods for the preparation of CNTs, such as, graphite-arc discharge method, Lijima has prepared CNTs by graphite-arc discharge method, and the as-prepared CNTs have lots of defects, and the sintered CNTs came into a bundle with many amorphous carbon impurities; another one is laser flash method. Smalley et al have for the first time achieved large amount production of single-walled CNTs by the laser flash method. This method is high cost, which is not easy for application and dissemination; other methods include catalytic pyrolysis, chemical vapor deposition, template method, hydrothermal method, condensed-phase electro-generated method, and so on. Currently, the CNTs prepared by either of these methods have some disadvantages, such as, high impurity, low yield, and high cost. These largely restrict the study and application of CNTs.
The macromolecular polymer based on the carbon skeleton can supply large amount of carbon resources for the preparation of CNTs. Polymers are widely used in our daily life, different businesses and high-grade technology field, because of their light weight, easy processing, aesthetic and practical features. On one hand, the polymer supply people enormous material progress; one the other hand, the waste generated from polymers raises several serious questions. In Chinese city, the waste plastics (500 million-600 million tons) accounts for about 4%-10% in the municipal solid waste every year, and this value is still growing by 8%-9% per year. At present, the recirculation of the waste plastics only account for 10%, and 90% of the waste plastics are landfilled and burned in China. Landfill takes a lot of land resources for long periods. The decomposition of the waste will also take a long time, and this will affect the permeability of air and water, damage the soil, affect the growth of plant, and waste a lot of resources. High-temperature incineration of these waste plastics damage the burning equipment easily, and is easy to produce dioxin, hydrogen chloride, heavy metals and some other toxic substances, which can cause secondary pollution. Therefore, the application of the waste plastic into the preparation of CNTs has important social and economic significance on saving energy, decreasing waste volume, and reducing harm to the environment.
The present invention uses hydrotalcite with better catalytic and carbonization properties to catalyze the polymer into CNTs through a thermal decomposition process. This method not only solve the problem of the waste plastics recycling, but also achieve the utilization of their resources, which significantly reduce the cost of the production of CNTs.